1. Field of the Invention
The present invention relates to accesses to SAN (Storage Area Network) disk storages, more specifically to an accessing system for disk storages that disperse the access load of each of those disk storages.
2. Description of Related Art
There is a well-known method in Japanese Unexamined Patent Publication (Kokai) JP 2000-099272 for sharing disk storages among a plurality of computers connected to those storages via a dedicated network such as fiber channel.
This technique is referred to as storage area network (SAN), which assures the high freedom in assignment of disk storages and computers so that a computer can be assigned to any of necessary disk storage areas flexibly.
In recent years, information handling systems that are accessed via the Internet are considered increasingly to be important. In particular, many computer systems have come to be built as Web servers for supplying various kinds of contents.
Such a Web server often includes an unspecific number of client computers, and accordingly it is accessed so frequently that it is difficult to estimate the peak time of accesses.
Japanese Unexamined Patent Publication (Kokai) JP 10-271447 and Japanese Unexamined Patent Publication (Kokai) JP 10-069467 disclose well-known methods for dispersing accesses to such a computer system so as to solve the above problem.
The JP 10-271447 reference discloses a technique for dividing for dispersing accesses in which each content is divided into small pieces so as to be stored in a plurality of disk storages.
In this case, the access load in proportion to the number of disk storages can be dispersed, but the technique cannot cope with accesses over an estimated value.
The JP 10-069467 reference also discloses a technique for dispersing the access load with use of a plurality of server computers, but it is still difficult to disperse the load of each disk storage.
The SAN enables a plurality of computers to share a plurality of disk storages, but it cannot maintain its performance when the number of computers increases excessively, since the load of each of the shared disk storages increases.